1. Field of the Invention
The invention relates to a method of starting up a steam system having several different pressure stages, at least one container for receiving a medium circulating in the plant being arranged at each pressure stage.
Furthermore, it relates to a drum-type heat-recovery boiler and a steam system containing a drum-type heat-recovery boiler for carrying out the method and also to a combined-cycle power station having such a steam system.
2. Description of the Prior Art
During the cold start of a thermal power station having a steam turbine and, for example, a drum-type heat-recovery boiler having several different pressure stages, the steam generated in the individual pressure stages is in each case drawn off via a bypass, when the cooling system is in operation, by the condenser, which is assigned to the steam turbine and through which cooling water flows, until the generated steam meets the requirements of the steam turbine and the further conditions for the start-up of the steam turbine have been fulfilled. However, a heat quantity transferred to the steam in the heat-recovery boiler is thus dissipated to the environment via the condenser or its cooling system. The bypass operation is therefore affected by losses. In addition, the heating surfaces, in particular at the boiler end on the exhaust-gas side, remain cold for a prolonged period.